Latticed Cd2+ Doping for Enhanced Ionic Transport in Li2ZrCl6 Solid-State Electrolytes toward High-Performance All-Solid-State Batteries

Halide solid-state electrolytes (SSEs) have emerged as a compelling research focus for advanced all-solid-state lithium-ion batteries (ASSLBs), driven by their concurrent possession of exceptional oxidation stability and remarkable mechanical deformability. While Li2ZrCl6 (LZC) has attracted significant attention for its cost-effectiveness and material abundance, its practical application remains a major challenge due to lower ionic conductivity. Herein, we reported a series of Cd2+-doped lithium-rich superionic conductors Li2+2xZr1–xCdxCl6 (0 ≤ x ≤ 0.2), which collectively adopted a Li3YCl6-like trigonal structure. The incorporation of Cd2+ ions, which possess a lower charge and larger ionic radius, enhanced carrier concentration and caused anisotropic lattice expansion. Specifically, Li2.1Zr0.95Cd0.05Cl6 (LZC-5Cd) exhibited the highest ionic conductivity (9.8 × 10–4 S cm–1) at 30 °C while simultaneously broadening the electrochemical window to 4.11 V. The ASSLBs configuration featuring the LiCoO2 cathode, LZC-5Cd electrolyte, and Li–In anode demonstrated superior reversible capacity (161.4 mAh g–1 at 0.1 C) within the wide potential range of 2.5–4.3 V and remarkable cycling stability (80.69% capacity retention over 250 cycles at 2 C). In this regard, this work presented a cost-effective structural engineering strategy that simultaneously boosted ionic conductivity and broadened the working potential range to provide a potential model for the large-scale application of halide-based ASSLBs.